A power conversion device includes: a first smoothing circuit connected to a first electric device; a second smoothing circuit connected to a second electric device; a first bridge circuit connected to the first smoothing circuit; a transformer having a primary side connected to a third electric device and a secondary side connected to the first bridge circuit and the second smoothing circuit; and a controller, wherein the controller varies a duty ratio of the first bridge circuit at a frequency higher than cutoff frequencies of the first and second smoothing circuits, controls a constant component of the duty ratio to control power exchange between the first and second electric devices, and controls a phase of a varying component of the duty ratio to control power exchange to and from the third electric device.